Purifier

ABSTRACT

In a system having a component ( 106 ) which is capable of reacting with a gaseous contaminant in a gas stream, a purifier assembly ( 102 ) is positionable in the gas stream and comprises a purifier medium ( 112 ) that reacts with the gaseous contaminant in a manner in which is substantially similar to the manner in which the component ( 106 ) reacts with the gaseous contaminant.

TECHNICAL FIELD

[0001] The present invention relates to devices and methods forpurifying gas streams. More particularly, the present invention relatesto devices and methods for removing contaminants, including gaseouscontaminants, from gas streams.

BACKGROUND OF THE INVENTION

[0002] In many industries, a high purity gas stream is used in a systemfor manufacturing a product. These systems may include a variety ofcomponents, including tubing, valves, orifices, and sensors, such asflow sensors, pressure sensors and temperature sensors. For example, inthe semiconductor industry, a high purity nitrogen gas stream may beused in a system for manufacturing silicon wafers. The system mayinclude an oxygen sensor for monitoring the amount of oxygen in thenitrogen gas stream, and the oxygen sensor may be made of a platinummetal.

[0003] Unfortunately, the high purity gas stream frequently containsgaseous contaminants which can adversely react, chemically orphysically, with the components of the system. Although the source ofthese gaseous contaminants may be external to the system, in manyinstances the gaseous contaminants are generated within the systemitself, e.g., during the process of manufacturing the product. Forexample, SiO₂ and other gaseous contaminants may be generated during theprocess for manufacturing the silicon wafers. These gaseous contaminantsmay be swept into the nitrogen gas stream and carried to the oxygensensor. The platinum metal in the oxygen sensor reacts with the gaseouscontaminants in the gas stream, damaging the oxygen sensor. This andother types of adverse reactions can occur with many components in manydifferent systems, and damaged components can seriously degrade thereliability of the products produced by any system. Consequently, thecomponents of these systems are subject to constant recalibration,extensive preventive maintenance, and frequent premature failure, whichresult in frequent shut downs that substantially reduce the efficiencyof the systems.

SUMMARY OF THE INVENTION

[0004] Embodiments of the present invention may address one or more ofthe previously described problems as well as many other problemsassociated with contaminants in gas streams.

[0005] In accordance with one aspect of the invention, a purifierassembly may be used in a system which has a component that is capableof reacting with a gaseous contaminant in a gas stream. The purifierassembly may be positioned in the gas stream upstream of the component,and the purifier assembly may comprise a bed of particulate material ora mass of fibrous material. The material of the purifier medium isselected to react with the gaseous contaminant in a manner which issubstantially similar to the manner in which the component reacts withthe gaseous contaminant, thereby reducing or even eliminating thegaseous contaminant in the gas stream.

[0006] In accordance with another aspect of the invention, a purifiermay be used in a system which has a component that is capable ofreacting with a gaseous contaminant in a gas stream. The purifier may bepositioned in the gas stream upstream of the component, and the purifiermay comprise a filter and a purifier medium. The filter removes particlecontaminants from the gas stream. The purifier medium is positioned inthe gas stream discrete from the filter. The purifier medium includes amaterial which is selected to react with the gaseous contaminant in amanner which is substantially similar to the manner in which thecomponent reacts with the gaseous contaminant, thereby reducing or eveneliminating the gaseous contaminant from the gas stream.

[0007] In accordance with another aspect of the invention, a purifierassembly for purifying a gas stream may comprise a purifier medium. Thepurifier medium may include a bed of particulate material or a mass offibrous material, and the material has at least a metal surface. Themetal of the purifier medium may be iron, ruthenium, osmium, cobalt,rhodium, iridium, nickel, palladium, platinum, copper, silver, gold,zinc, vanadium, and chromium and mixtures thereof.

[0008] In accordance with another aspect of the invention, a purifierfor removing contaminants from a gas stream may comprise a housing, apurifier assembly, and a filter. The housing may have an inlet and anoutlet and define a gas flow path between the inlet and the outlet. Thepurifier assembly may be disposed in the housing in the gas flow pathdiscrete from the filter. The purifier assembly may include a purifiermedium having a metal surface which is capable of reacting with gaseouscontaminants in the gas stream. The filter is disposed in the housing inthe gas flow path and removes particle contaminants from the gas stream.

[0009] In accordance with another aspect of the invention, a method ofprotecting a component capable of reacting with a gaseous contaminant ina gas stream comprises passing the gas stream through a purifier mediumbefore the gas stream is directed past the component. Passing the gasstream through the purifier medium includes passing the gas streamthrough a bed of particulate or a mass of fibrous material that reactswith the gaseous contaminants in a manner substantially similar to themanner in which the component reacts with gaseous contaminants, therebyreducing or even eliminating gases components from the gas stream.

[0010] Devices and method embodying the invention may include one ormore of these various aspects of the invention. Embodiments whichfeature a purifier medium having a material or a metal surface thatreacts with the gaseous contaminants in the gas stream protectcomponents of the system very effectively. The purifier medium may belocated upstream of the component, so the gaseous contaminants reactwith the purifier medium first. In reacting with the gaseouscontaminants, the purifier medium may pull the gaseous contaminants outof the gas stream or otherwise render the gaseous contaminants incapableof damaging the component. Consequently, a highly purified gas streamcontinues past the purifier medium and past the component withoutcausing any damage to the component.

DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a cross sectional view of one example of a purifier in asystem with a component.

DESCRIPTION OF EMBODIMENTS

[0012] Devices and methods which purify gas streams in accordance withthe invention may be used to protect one or more components of a systemfrom gaseous contaminants in a gas stream. Any component of a system incontact with the gas stream may be protected, including, for example,tubing walls, valves, orifices, sensors, and transducers. The gas streammay comprise, for example, any process gas, including high purityprocess gases such as nitrogen, argon, hydrogen, and helium. The gaseouscontaminants may include a wide variety of gases, including, forexample, organometalic compounds such as arsine, phosphine, and siliconcontaining gases, e.g., SiO₂. Other gaseous contaminants may includecarbon dioxide and hydrocarbons.

[0013] The component may adversely react to the gaseous contaminants ina wide variety of ways, both physically and chemically. For example, thegaseous contaminant may plate, condense, coalesce, adsorb, absorb orotherwise be deposited onto one or more materials of the component inthe gas stream. Alternatively or additionally, the gaseous contaminantmay oxidize, reduce, form a complex with, or catalyze a reaction withthe material of the component. A purifier embodying the invention may beoperatively associated with the component, e.g., by inserting thepurifier in the gas stream upstream of the component. In preferredembodiments, the purifier may include a purifier medium that will beaffected by the gaseous contaminant in much the same way that thematerial of the component being protected would otherwise be affected,thereby sacrificially protecting the component. For example, thepurifier medium may react with a gaseous contaminant in a mannersubstantially similar to the manner in which the component wouldotherwise react to the gaseous contaminant, thereby pulling the gaseouscontaminant from the gas stream or otherwise rendering the gaseouscontaminant incapable of damaging the component, for example, byaltering the physical or chemical properties of the gaseous contaminant.

[0014] Purifiers embodying the invention may be configured in a widevariety of ways. One example of a purifier 100 is shown in cross sectionof FIG. 1. Generally, the purifier 100 may include a housing 101 and apurifier assembly 102 operatively associated with the housing 101. Thehousing may be formed from any suitably impervious material which iscompatible with the gas stream, including, for example, a polymericmaterial or a metal such as stainless steel. The housing 100 preferablyincludes at least one inlet 103 and at least one outlet 104 and definesa gas flow path between the inlet 103 and the outlet 104. However, thehousing is not limited to any particular shape. For example, the housingmay be designed as a top mount assembly or a T-type assembly for themicroelectronics industry and may include both the inlet and the outleton the same end of the housing. In the illustrated embodiment, thehousing 101 may be designed as in-line assembly having a cylindricalconfiguration with the inlet 103 at one end and the outlet 104 at theopposite end. The inlet 103 and the outlet 104 may be configured asfittings and may be joined to corresponding fittings in a gas supplyline 105 which may fluidly communicate with the component 106 of thesystem to be protected. Further, the housing may comprise a one-piece ormulti-piece structure. For example, the housing may include a bodydefining a cavity for the purifier assembly and a head or basedetachably or permanently mounted to the body. In the illustratedembodiment, the housing 101 preferably comprises two hollow, generallycylindrical portions, e.g., an inlet portion 110 and an outlet portion111, which may be permanently coupled, e.g., bonded or welded.

[0015] The purifier assembly may be cooperatively arranged with thehousing in a variety of ways. For example, the purifier assembly may bemounted to the housing at the inlet and/or the outlet or within thehousing. The purifier assembly may be the sole component within thehousing, or the housing may include the purifier assembly and one ormore additional components, such as the component to be protected. Forexample, the purifier assembly may be mounted near the inlet of thehousing and the component to be protected by the purifier assembly maybe mounted inside the housing between the inlet and the outlet. Thepurifier assembly may be fitted to the housing in a variety of ways, forexample, the purifier assembly may be removably mounted or permanentlymounted to or in the housing. The purifier assembly is preferably fittedto or in the housing completely across the gas flow path or the gasstream. However, the purifier assembly may be disposed in the gas streamnot completely across the gas stream but in sufficient contact with thegas stream to remove or otherwise render harmless a sufficient amount ofthe gaseous contaminants to protect the downstream component. In theillustrated embodiment, the purifier assembly 102 is preferably disposedcompletely across the gas flow path defined by the housing 101 andpermanently attached to the housing 101, e.g., by bonding or welding thepurifier assembly 102 to the housing 101.

[0016] The purifier assembly may be variously configured. For example,the purifier assembly may have a generally disc-shaped configuration ora solid generally cylindrical configuration through which the gas streammay pass axially. As another example, the purifier may have a hollowgenerally cylindrical configuration through which the gas stream maypass radially inside-out or outside-in. As yet another example, thepurifier assembly may have a generally cup-shaped configuration. Thecross section of any of these configurations may be regular, e.g.,circular or polygonal, or may be irregular. In the illustratedembodiment, the purifier assembly 102 preferably has a generallydisc-shaped configuration with a generally circular cross section.Further, the purifier assembly may be configured as a single piecestructure or a multi-piece structure. The purifier assembly preferablycomprises one or more purifier media and may comprise additionalstructures for supporting the one or more purifier media, for example,within the housing. In the illustrated embodiment, the purificationassembly 102 includes a purifier medium 112 contained by an annular ringor spool 113 and upstream and downstream porous barriers 114, 115.However, the supporting structures may vary widely from one purifierassembly to another depending, for example, on the nature of thepurifier medium. In some embodiments, the housing may support thepurifier medium without any additional supporting structures.

[0017] The purifier medium preferably comprises a material that will beaffected by gaseous contaminants in the gas stream in a mannersubstantially similar to the way in which the material of the componentbeing protected would otherwise be affected by the gaseous contaminants.Thus, the material of the purifier medium may be identical to thematerial of the component being protected or analogous to the materialof the component being protected, i.e., capable of reacting to thegaseous component in a substantially similar manner. Two or morepurifier media may be included, for example, where different componentswithin the system are to be protected. For many embodiments, thematerial of the purifier medium preferably comprises a metal, mostlyincluding, for example, noble metals and Group VIII metals. Morepreferably, the metal of the purification medium may comprise one ormore of the following metals: iron, ruthenium, osmium, cobalt, rhodium,iridium, nickel, palladium, platinum, copper, silver, gold, zinc,vanadium, and chromium and mixtures of these metals. The material of thepurification medium may include only a single constituent, e.g., asingle metal, or may be combined with various other constituents,including additional metals and/or non-metals such as sorbents andcatalysts.

[0018] The purification medium may comprise any suitable form. Forexample, the purification medium 112 may be in the form of one or moremasses of fibrous material, such as a mat, a gauze, a wool, a non-wovenweb, or a mesh, e.g., a woven web, in one or more layers. The fibers ofthe fibrous material have any suitable diameter, e.g., several thousandsof an inch or less, and any suitable length, e.g., several inches orless. The fibers may be a substantially pure form of the purifiermaterial selected to react with the gaseous contaminants. For example,each fiber may entirely consist of a metal. Alternatively, each fibermay comprise a combination of the selected purifier material and one ormore other materials. Preferably, however, the fiber at least includesthe selected purifier material as a surface which may be contacted bythe gas stream. For example, each fiber may comprise a metal, ceramic,or polymeric base material coated with the selected purifier material inany suitable manner. The mass of fibrous material is preferablycompressed to provide a uniform density. Even more preferably, the massof fibrous material may be fashioned as a preform, e.g., a fibrousstructure having predetermined dimensions, and the preform may have anysuitable configuration such as a disc-shaped configuration or acylindrically shaped configuration.

[0019] Alternatively, the purification medium 112 may comprise one ormore beds of particulate material. The particulate material may bebeaded, granular, or powdery, and the individual particles may havevarious regular or irregular shapes including dendritic, acicular,fibril, and spherical. The particles may be a substantially pure form ofthe purifier material selected to react with the gaseous contaminants.For example, each particle may entirely consist of a metal.Alternatively, each particle may comprise a combination of the selectedpurifier material and one or more other materials. Preferably, however,the particle at least includes the selected material as a surface whichmay be contacted by the gas stream. For example, the particles maycomprise a metal, ceramic, or polymeric base material coated with theselected purifier material in any suitable manner. The nominal size andamount of the particulate material and the size of the particulate bedmay vary widely, depending on such factors as the desired capacity andefficiency of the bed and the desired flow parameters, e.g., pressuredrop and flow rate, through the bed. In some embodiments, size of theparticulate material may be less than about {fraction (1/20)}th of thelateral dimension, e.g., diameter, of the particulate bed, morepreferably less than about {fraction (1/100)}th of the lateraldimension. Further, the bed of particulate material may be immobilized,for example, by a binder or in a fibrous matrix or by sinter bonding theparticles to one another and/or a substrate. Preferably, the particlesof the bed are not bonded to one another but are packed within the bedsufficiently tightly to prevent the bed from fluidizing and/or formingchannels in the bed as the gas stream flows through the bed. The bed ofparticulate material may completely fill the housing, or the particulatematerial may occupy less than the internal volume of the housing.

[0020] In the illustrated embodiment, the purifier medium 112 preferablycomprises a bed of particulate material which may be radially containedwithin the annular ring 113. For example, the purification medium 112may comprise a bed of particulate material tightly packed within theannular ring 113. The inner diameter of the annular ring may be greaterthan the inner diameter of the housing but is preferably substantiallyequal to or, even more preferably, somewhat less than the inner diameterof the housing 101. The thickness and the inner diameter of the annularring 113 may vary depending on factors such as the amount and size ofthe particulate material to be contained within the bed. For example,the bed of particulate material may have a diameter of about 0.75 inchor less, e.g., about 0.50 inch or less, and a thickness of about 0.250inch or less, e.g., about 0.125 inch or less, and the bed may containabout 3 grams or less, e.g., about 2 grams or less, of metal particleshaving a size of about 100μ or less, e.g., in the range from about 10μto about 45μ. For embodiments intended to protect an oxygen sensorhaving a platinum surface in the gas stream, particles of platinummetal, such as those available from Alfa Aesar, A Johnson MattheyCompany of Ward Hill, Mass., may be selected for the purifier material.

[0021] The porous barriers 114, 115 are preferably disposed on bothsides of the bed to axially contain particulate material within the bed.The porous barriers may be bonded, e.g., welded along their edges, andcompletely contain the bed of particulate material without significantadditional structure. In the illustrated embodiment, the porous barriersare cooperatively arranged with additional supporting structure, such asthe annular ring 113, to contain the bed of particulate material, e.g.,within the interior of the annular ring 113. The size of the openings inthe porous barrier 114, 115 depends on the size of the particulatematerial in the bed, finer particulate material indicating smalleropenings in the porous barrier. The porous barrier may comprise anysuitably porous structure such as a fibrous web, a mesh, a porousmembrane or a porous composite material, and may be formed from anysuitable material such as metal or polymer. In the illustratedembodiment, the upstream porous barrier 114 preferably comprises aporous composite material including a layer of PMF™ 316L stainless steelporous medium sandwiched between layers of sintered Rigimesh® (Grade K)porous medium having a composite gaseous removal efficiency of about10e2 at 0.4 microns.

[0022] The downstream porous barrier 115 may be identical or similar tothe upstream porous barrier 114. However, in many embodiments, thedownstream porous barrier may comprise a high efficiency filter having agaseous removal efficiency, for example, on the order of 10e4, morepreferably on the order of 10e6, and even more preferably on the orderof 10e9, for 3 nanometer particles. A high efficiency filter isavailable from Pall Corporation under the trade designation MiniULTRAMET-L™ 1100 Series Assembly. A high efficiency filter not onlyserves to contain the particles of purification material within the bed,it also removes solid contaminants from the gas stream. While thepurifier medium 112 is preferably located upstream of the highefficiency filter, it may be located downstream of the high efficiencyfilter or it may be sandwiched between portions of the high efficiencyfilter. However, in preferred embodiments, the purifier medium, whetherupstream, downstream or within the high efficiency filter, is disposedin the gas stream discrete from the high efficiency filter, e.g., thepurifier medium and the filter are preferably positioned at discretelocations within the gas stream. Combining the purifier medium with thehigh efficiency filter, e.g., by coating the high efficiency filter withthe selected purification material, may result in design trade offs anddegraded performance.

[0023] The purifier may be fabricated in a wide variety of waysdepending, for example, on the desired configuration of the purifier andthe nature of the purifier medium. For example, in the illustratedembodiment, the downstream porous barrier 115, e.g., the high efficiencyfilter may be joined between the open end of the outlet portion 111 ofthe housing 101 and a rim of the annular ring 113. These components arepreferably joined by a bond, e.g., an adhesive or solvent bond, or, morepreferably, a weld, which seals them to one another, seals the outeredge of the downstream porous barrier 115, and forces the downstreambarrier 115 tightly against the face of the annular ring 113, defining apocket between the downstream porous barrier 115 and the wall of theannular ring 113.

[0024] The purifier medium 112 may be selected in accordance with thematerial of a component to be protected and then positioned in thepocket. For example, a mass of fibrous material selected in accordancewith the component being protected may be positioned in the pocket. Inparticular, a preform of the fibrous mass having dimensionscorresponding to, e.g., slightly larger than, the dimensions of thepocket may be inserted in the pocket, preferably, with a interferencefit between the edge of the preform and the inner wall of the annularring. Alternatively, a bed of particulate material selected inaccordance with the component to be protected may be deposited withinthe pocket. The particular material may be wet laid in the pocket on thedownstream porous barrier 115 but is preferably dry laid in any suitablemanner. For example, an amount of the selected particulate material maybe dry laid in the pocket and compacted, e.g., by vibrations and/orforce, to pack the bed. An additional amount of selected particulatematerial may then again be dry laid and compressed, and this process maycontinue until the pocket is filled or, more preferably, slightlyoverfilled, with a packed bed of selected particulate material.

[0025] Once the purifier medium has been disposed in the pocket of theannular ring 113, the upstream porous barrier 114 may be joined betweenthe open end of the inlet portion 110 of the housing 101 and theopposite rim of the annular ring 113. Again, these components arepreferably joined by a bond or a weld which seals them to one another,seals the outer edge of the upstream porous barrier 114, and forces theupstream porous barrier 114 tightly against the face of the annular ring113, tightly confining the purifier medium 112 within the pocket of theannular ring 113.

[0026] Once the purifier is fabricated, it may be positioned in the gasstream upstream from the component 106 to be protected, for example, byinserting the purifier into the gas supply line 105. The gas streampasses along the gas supply line 105 through the purifier 100, and asubstantial portion of, preferably all of, the gas in the gas streamcontacts, e.g., passes through, the purifier medium 112. The gaseouscontaminants in the gas stream react with the purifier medium 112 in amanner substantially similar to the manner in which the material of thecomponent 106 would otherwise react with the gaseous contaminants. Byreacting with the gaseous contaminants in a manner similar to that ofthe component 106, the purifier medium 112 may pull the gaseouscontaminants out of the gas stream, substantially reducing the amount ofgaseous contaminants in the gas stream and/or may otherwise render thegaseous contaminants incapable of harming the component 106, forexample, by chemically reacting with the gaseous contaminants andtransforming the gaseous contaminants into substances which are notharmful to the component 106.

[0027] From the purifier medium 112, the gas stream may pass through thehigh efficiency filter and then past the component 106. Because the gasstream has been purified by the purifier medium 112, the component 106remains unharmed by the gas stream. The component 106 thus functionsmore reliability for a much longer period of time, eliminating frequentshutdowns for recalibrating, maintaining and/or replacing a damagedcomponent. Consequently, the system operates much more efficiently andreliably.

[0028] While the invention has been described in some detail by way ofvarious embodiments, the invention is susceptible to variousmodifications and alternative forms and is not restricted to thespecific embodiments previously described and illustrated. For example,a purifier assembly may include both a mass of fibrous material and abed of particulate material, either separate or dispersed within oneanother. Further, in the illustrated embodiment, the purifier assemblycomprises a purifier medium disposed across the gas flow path and spacedfrom the component being protected. Alternatively, the purifier assemblymay comprise any other porous structure which includes the purificationmedium and encapsulates or otherwise covers the component and protectsthe component from gaseous contaminants in the fluid stream. Forexample, the purifier assembly may comprise a porous jacket which isformed from or coated with the material selected to protect thecomponent. Thus, the specific embodiments disclosed are not intended tolimit the invention, but on the contrary the invention is intended tocover all modifications equivalence and alternatives falling within thespirit and scope of the inventions defined by the following claims.

[0029] All references cited herein including publications, patents, andpatent applications, are hereby incorporated in there entireties byreference.

What is claimed is:
 1. In a system having a component which is capableof reacting with a gaseous contaminant in a gas stream, a purifierassembly positionable in the gas stream upstream of the component andcomprising a purifier medium which includes at least one of a bed ofparticulate material and a mass of fibrous material, wherein thematerial of the purifier medium reacts with the gaseous contaminant in amanner which is substantially similar to the manner in which thecomponent reacts with the gaseous contaminant, thereby reducing thegaseous contaminant in the gas stream.
 2. The purifier assembly of claim1 wherein the purifier medium comprises a bed of particulate material,particles of the particulate material having at least a metal surfaceand a size less than about 100μ.
 3. The purifier assembly of claim 2wherein the metal is selected from the group consisting of iron,ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium,platinum, copper, silver, gold, zinc, vanadium, and chromium andmixtures thereof.
 4. The purifier assembly of claim 2 wherein the bed ofparticulate material comprises a packed bed of unbonded platinumparticles having a size less than about 100μ and the purifier assemblyfurther comprises porous barriers upstream and downstream of the bed tocontain the platinum particles.
 5. The purifier assembly of claim 1wherein the purifier medium comprises a mass of fibrous material,wherein fibers of the fibrous material have at least a metal surface. 6.The purifier assembly of claim 5 wherein the mass of fibrous materialcomprises a preform.
 7. A purifier for use in a system which has acomponent that is capable of reacting with a gaseous component in a gasstream, the purifier being positionable in the gas stream upstream ofthe component and comprising a filter and a purifier medium, wherein thepurifier medium is positioned in the gas stream discrete from the filterand the purifier medium includes a material that reacts with the gaseouscontaminant in a manner which is substantially similar to the manner inwhich the component reacts with the gaseous contaminant.
 8. The purifierof claim 7 wherein the filter comprises a high efficiency filter.
 9. Thepurifier of claim 8 wherein the high efficiency filter has a gaseousremoval efficiency on the order of 10e9 for 3 nanometer particles. 10.The purifier of any one of claim 7-9 wherein the purifier mediumcomprises a bed of particles having at least a metal surface and a sizeless than about 100μ the metal being selected from the group consistingof iron, ruthenium, osmium, cobalt, rhodium, iridium, nickel, palladium,platinum, copper, silver, gold, zinc, vanadium, and chromium andmixtures thereof.
 11. The purifier of claim 10 wherein the metalcomprises platinum.
 12. The purifier of any one of the claims 7-9wherein the purifier medium comprises a mass of fibrous material,wherein fibers of the fibrous material have at least a metal surface,the metal being selected from the group consisting of iron, ruthenium,osmium, cobalt, rhodium, iridium, nickel, palladium, platinum, copper,silver, gold, zinc, vanadium, and chromium and mixtures thereof.
 13. Thepurifier of claim 12 wherein the mass of fibrous material comprises apreform.
 14. A purifier assembly for purifying a gas stream, thepurifier assembly comprising a purifier medium which includes at leastone of a bed of particulate material and a mass of fibrous material,wherein the material has at least a metal surface and the metal isselected from the group consisting of iron, ruthenium, osmium, cobalt,rhodium, iridium, nickel, palladium, platinum, copper, silver, gold,zinc, vanadium, and chromium and mixtures thereof.
 15. The purifierassembly of claim 14 wherein the metal comprises platinum
 16. Thepurifier assembly of claim 14 or 15 wherein the purifier medium includesa bed of particulate material, wherein particles of the particulatematerial have a size less than about 100μ.
 17. The purifier assembly ofclaim 14 or 15 wherein the purifier medium includes a mass of fibrousmaterial comprising a preform.
 18. A purifier for removing contaminantsfrom a gas stream, the purifier comprising a housing having an inlet andan outlet and defining a gas flow path between the inlet and the outlet,a filter disposed in the housing in the gas flow path to remove particlecontaminants, and a purifier assembly cooperatively arranged within thehousing in the gas flow path discrete from the filter, wherein thepurifier assembly includes a purifier medium having at least a metalsurface capable of reacting with a gaseous contaminant in the gasstream.
 19. The purifier medium of claim 18 wherein the purifierassembly is disposed in the housing.
 20. The purifier of claim 18 or 19wherein the purifier medium is positioned upstream of the filter. 21.The purifier of claim 18, 19, or 20 wherein the purifier mediumcomprises a bed of particulate metal, the metal being selected from thegroup consisting of iron, ruthenium, osmium, cobalt, rhodium, iridium,nickel, palladium, platinum, copper, silver, gold, zinc, vanadium, andchromium and mixtures thereof and particles of the metal having a sizeless than about 100μ.
 22. The purifier assembly of any one of claims18-21 wherein the filter comprises a high efficiency filter.
 23. Amethod of protecting a component capable of reacting with a gaseouscontaminant in a gas stream comprising contacting the gas stream with apurifier medium upstream from the component, wherein contacting the gasstream with the purifier medium includes contacting the gas stream withat least one a bed of particulate material and a mass of fibrousmaterial that reacts with the gaseous contaminant in a manner which issubstantially similar to the manner in which the component reacts withthe gaseous contaminant.
 24. The method of claim 23 wherein contactingthe gas stream with the purifier medium includes passing substantiallyall of the gas in the gas stream through the purifier medium.